Routing, Code, and Spectrum Assignment, Subcarrier Spacing, and Filter Configuration in Elastic Optical Networks [Invited]

In elastic optical networks (EONs), the modulation format can be configured to guarantee the required optical reach with efficient spectrum utilization. For this reason, the literature related to EONs has treated the problem of routing and spectrum assignment together with the problem of modulation format assignment. Recently, in addition to modulation format, code adaptation has also been successfully demonstrated to provide adequate spectrum utilization given a target optical reach. This paper presents the concept of routing, code, and spectrum assignment (RCSA) for EONs. We propose the optimization of multiple transmission parameters including code, subcarrier spacing, and filters' passband to avoid detrimental filtering effects. Measurements are carried out in an EON testbed to identify the relation between transmission parameters and the number of traversed filters and optical reach. Then, the measurements are used as inputs in simulations to test RCSA. The simulations show that code adaptation reduces blocking probability with respect to format adaptation. Another interesting result shows that the use of several possibilities for the transmission parameter setting may induce high spectrum fragmentation.